Composition for forming porous film, porous film and method for forming the same, interlevel insulator film

Abstract

Provided is a coating liquid which can easily form a porous film having desirably controlled thickness by the method used for a usual semiconductor process, and having an excellent mesopore channel structure. Specifically provided is a composition for forming porous film comprising a surfactant, an aprotic polar solvent and a solution comprising a polymer formed by hydrolysis and condensation of one or more silane compounds represented by foramula (1): RnSi(OR′)_4-n. Also provided is a method for manufacturing a porous film comprising steps of applying said composition so as to form a film, drying the film and transforming the dried film to a porous film by removing said surfactant. The porous film obtained from the composition for forming porous film is further provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a composition for film formation which can be formed into a porous film which excels in dielectric properties, adhesion, film uniformity and mechanical strength, and has reduced moisture absorption; a porous film and a method for forming the same; and a semiconductor device which contains the porous film inside.[0003]2. Description of the Related Art[0004]In the fabrication of semiconductor integrated circuits, as the circuits are packed tighter, an increase in interconnection capacitance, which is a parasitic capacitance between metal interconnections, leads to an increase in interconnection delay time, thereby hindering the enhancement of the performance of semiconductor circuits. The interconnection delay time is called an RC delay which is in proportion to the product of the electric resistance of the metal interconnections and the static capacitance between the interconnections. Red...

AI Technical Summary

Benefits of technology

[0030]Thus, keeping the mechanical strength of the semiconductor device secured, the hygroscopic property of the porous film is decreased. Hence, the semiconductor device with a built-in insulator film having a low dielectric constant is obtained. Because of lowering dielectric constant of the insulator film, the parasitic capacitance of the area around the multi-level interconnects is decreased, leading to the high-speed operation and low power consumption of the semiconductor device.

[0031]Moreover, it is preferable for the semiconductor device of the invention that said porous film is between metal interconnections in a same layer of multi-level interconnects or between upper and lower metal interconnection layers. This arrangement can achieve a high-performing and highly reliable semiconductor device.

[0032]Use of the composition for forming a porous film of the invention facilitates the formation of a porous film having a stable mesoporous channel structure at a desirably controlled thickness. The porous film has a low dielectric constant, and excels in adhesion, film uniformity, and mechanical strength. In addition, use of the porous film formed by the composition of the invention as the insulator film of the multi-level interconnects can produce a high-performing and highly reliable semiconductor device.

Problems solved by technology

In the fabrication of semiconductor integrated circuits, as the circuits are packed tighter, an increase in interconnection capacitance, which is a parasitic capacitance between metal interconnections, leads to an increase in interconnection delay time, thereby hindering the enhancement of the performance of semiconductor circuits.

However, use of this structure alone has limits in the enhancement of the performance, so the reduction in interconnection capacitance is an urgent necessity for higher performance of semiconductors.

However, these methods have respective major drawbacks as follows.

In the first method for forming a porous film, the synthesis of the precursor solution of the siloxane polymer increases the cost.

In addition, the formation of the coating film by coating the precursor solution increases the amount of silanol groups remaining in the coating film, which causes a degassing phenomenon indicating the evaporation of water and the like in the heat treatment process that is conducted later and which also deteriorates the film quality due to the porous film absorbing humidity.

In the second method for forming a porous film, the speed control of the evaporation of the solvent from the wet gel requires a special type of coating device, which increases the cost.

In addition, a significant amount of silanol remains on the surface of the micro-pores which must be silanized because otherwise hygroscopicity is high so that the film quality decreases.

The silanization makes the process more complicated.

In the case where a wet gel is formed by the CVD process, it is necessary to use a special type of CVD device which is different from the plasma CVD device generally used in the semiconductor process, thereby also increasing the cost.

This makes it difficult to set the relative permittivity of the porous film to 2 or below.

However, it is not preferable because it makes the manufacturing process complicated and increases the cost.

However, these methods have problems as follows.

In the first method, the powdered porous member can be easily formed, but it is impossible to form a porous film as a thin film on the substrate which is used for the fabrication of semiconductor devices.

In the second method, a porous member can be formed into a thin film, but it is impossible to control the orientation of micro-pores, and it is also impossible to form a uniform thin film in a wide area.

However, in this method, too, the restriction of the solute concentration makes it difficult to properly control the thickness of a coating film, thereby making it difficult to apply it to a practical semiconductor fabrication process.

When this solution is diluted with water, the thickness of the coating film becomes controllable, but the speed of polycondensation of the silica component increases to lose stability of the coating solution.

As mentioned above, the conventional materials have several problems such as deterioration of the film quality during the heat treatment step and high cost.

Moreover, the formation of the porous film results in pores having a large diameter so that it is difficult to obtain the low dielectric constant.

When the conventional porous film is incorporated into the multi-level interconnects of the semiconductor device as an insulator film, there is a problem that the mechanical strength necessary for the semiconductor device is not obtained.

Thus, when the dielectric constant of the porous film used as an insulator film in the multi-level interconnects of the semiconductor device is too high, the RC delay in the multi-level interconnects of the semiconductor device is increased so that the performance of the semiconductor device (high speed and low power consumption) cannot be improved.

This represent large problems.

Furthermore, a porous film with a low mechanical strength deteriorates the reliability of the semiconductor device.

Images